The purpose of this investigation is to critically examine the elements that support erythropoiesis and the regulatory mechanisms that control it. This is accomplished through analysis of the action of mutant genes that alter the normal growth and development of blood-forming tissue. In my laboratory, 11 of the 14 known hereditary anemias of mice are currently under study. They provide the material necessary for a comparative, developmental, biochemical, and genetical analysis of erythropoiesis. The information obtained from these studies permits us to develop a generalized picture of normal blood formation and yields insight into the nature of the regulatory mechanisms. The investigation provides us with a basis for formulating therapeutic approaches to derangements in erythropoiesis produced by genetic, pharmaceutical, or environmental agents. The essential aim of this investigation is to develop new analytical methods and to devise new and improved techniques for the therapy of human perinatal disorders of erythropoiesis.